Turbomachine plasma seal system

ABSTRACT

Various embodiments include a turbomachine with a plasma seal system. The turbomachine can include: a diaphragm section having: an axially facing diaphragm wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing bucket wall opposing the axially facing diaphragm wall; and a seal member extending from the axially facing bucket wall, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.

FIELD OF THE INVENTION

The subject matter disclosed herein relates to power systems. Moreparticularly, the subject matter relates to turbomachine-based powersystems.

BACKGROUND OF THE INVENTION

Conventional turbomachines, e.g., gas turbomachines extract energy fromfluid flow (e.g., gas fluid flow). One interest in turbomachine designis to provide high efficiency for energy generation. A turbine typicallyexperiences efficiency loss due to working fluid leakage through aclearance gap between a turbine blade and a nozzle diaphragm in aturbine stage. The gap between the turbine blade and the casing canallow the working fluid (primary flow) to mix with a cooling fluid path(secondary flow), and decrease the efficiency of the turbine.

BRIEF DESCRIPTION OF THE INVENTION

Various embodiments of the invention include a turbomachine with aplasma seal system. In some cases, the turbomachine can include: adiaphragm section having: an axially facing diaphragm wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing bucketwall opposing the axially facing diaphragm wall; and a seal memberextending from the axially facing bucket wall, wherein the seal memberaxially overlaps a portion of the discourager seal of the diaphragmsection leaving a radial gap between the seal member and the discouragerseal; and a plasma generator coupled to the diaphragm section forgenerating a plasma which reduces the radial gap between the seal memberand the discourager seal.

A first aspect of the invention includes a turbomachine having: adiaphragm section having: an axially facing diaphragm wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing bucketwall opposing the axially facing diaphragm wall; and a seal memberextending from the axially facing bucket wall, wherein the seal memberaxially overlaps a portion of the discourager seal of the diaphragmsection leaving a radial gap between the seal member and the discouragerseal; and a plasma generator coupled to the diaphragm section forgenerating a plasma which reduces the radial gap between the seal memberand the discourager seal.

A second aspect of the invention includes a turbomachine having: adiaphragm section having: an axially facing diaphragm wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing bucketwall opposing the axially facing diaphragm wall; and a seal memberextending from the axially facing bucket wall, wherein the seal memberaxially overlaps a portion of the discourager seal of the diaphragmsection leaving a radial gap between the seal member and the discouragerseal; a fluid channel extending between the axially facing diaphragmwall and the axially facing bucket wall, the fluid channel intersectingwith the radial gap; and a plasma generator coupled to the diaphragmsection for generating a plasma which reduces the radial gap between theseal member and the discourager seal.

A third aspect of the invention includes a method including: providing aturbomachine having: a diaphragm section having: an axially facingdiaphragm wall; and a discourager seal protruding axially from theaxially facing diaphragm wall; a rotor section having: a bucket havingan axially facing bucket wall opposing the axially facing diaphragmwall; and a seal member extending from the axially facing bucket wall,wherein the seal member axially overlaps a portion of the discouragerseal of the diaphragm section leaving a radial gap between the sealmember and the discourager seal; and a plasma generator coupled to thediaphragm section; and actuating the plasma generator to generate aplasma which reduces the radial gap between the seal member and thediscourager seal, wherein the plasma further reduces an axial gapbetween the discourager seal a radially extending portion of the sealmember.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a schematic partial cross-sectional depiction of aturbomachine (e.g., a gas turbine) according to various embodiments ofthe invention.

FIG. 2 shows a close-up schematic depiction of components of theturbomachine of FIG. 1 according to various alternative embodiments ofthe invention.

FIG. 3 shows a flow diagram illustrating processes in a method accordingto various embodiments of the invention.

It is noted that the drawings of the invention are not necessarily toscale. The drawings are intended to depict only typical aspects of theinvention, and therefore should not be considered as limiting the scopeof the invention. In the drawings, like numbering represents likeelements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As noted, the subject matter disclosed herein relates to power systems.More particularly, the subject matter relates to turbomachine-basedpower systems and fluid flow within those systems. In particular,aspects of the invention relate to gas turbomachines (also referred toas gas turbines).

As described herein, conventional turbomachines, e.g., gasturbomachines, extract energy from fluid flow (e.g., gas fluid flow).One interest in turbine design is to provide high efficiency for energygeneration. A turbine typically experiences efficiency loss due toworking fluid leakage through a clearance gap between a turbine bladeand a nozzle diaphragm in a turbine stage. The gap between the turbineblade and the casing can allow the working fluid (primary flow) to mixwith a cooling fluid path (secondary flow), and decrease the efficiencyof the turbine.

In order to address these conventional concerns, various embodiments ofthe invention include turbomachine (e.g., gas turbine) plasma sealsystems. The plasma seal systems disclosed according to variousembodiments of the invention include a plasma generator operablyconnected (e.g., mounted) on a portion of the gas turbine diaphragm. Inparticular embodiments, the plasma generator is mounted on thediscourager seal of the diaphragm to prevent mixing of the primary(working fluid) flow with the secondary (cooling fluid) flow in theturbomachine. The plasma generator creates a plasma seal between the“angel wing” seal of the rotor and the discourager seal (flow guide) ofthe turbomachine diaphragm. In particular, the plasma generator can beconfigured to generate a plasma (e.g., a plasma coating or layer)between the discourager seal and the angel wing seal to reduce theradial gap between these components. This helps to define the twodistinct fluid flow paths (working fluid v. cooling fluid), therebyenhancing the mechanical work performed by the working fluid.

Various particular embodiments of the invention include a turbomachinehaving: a diaphragm section including: an axially facing wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing wallopposing the axially facing wall of the diaphragm section; and a sealmember extending from the axially facing wall of the bucket, wherein theseal member axially overlaps a portion of the discourager seal of thediaphragm section leaving a radial gap between the seal member and thediscourager seal; and a plasma generator coupled to the diaphragmsection for generating a plasma which reduces the radial gap between theseal member and the discourager seal.

Various additional embodiments of the invention include a turbomachinehaving: a diaphragm section having: an axially facing wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing wallopposing the axially facing wall of the diaphragm section; and a sealmember extending from the axially facing wall of the bucket, wherein theseal member axially overlaps a portion of the discourager seal of thediaphragm section leaving a radial gap between the seal member and thediscourager seal; a fluid channel extending between the axially facingwall of the diaphragm section and the axially facing wall of the bucket,the fluid channel intersecting with the radial gap; and a plasmagenerator coupled to the diaphragm section for generating a plasma whichreduces the radial gap between the seal member and the discourager seal.

Various other embodiments of the invention include a method including:providing a turbomachine having: a diaphragm section having: an axiallyfacing wall; and a discourager seal protruding axially from the axiallyfacing diaphragm wall; a rotor section having: a bucket having anaxially facing wall opposing the axially facing wall of the diaphragmsection; and a seal member extending from the axially facing wall of thebucket, wherein the seal member axially overlaps a portion of thediscourager seal of the diaphragm section leaving a radial gap betweenthe seal member and the discourager seal; and a plasma generator coupledto the diaphragm section; and actuating the plasma generator to generatea plasma which reduces the radial gap between the seal member and thediscourager seal, wherein the plasma further reduces an axial gapbetween the discourager seal a radially extending portion of the sealmember.

As will be described herein, generating plasma in the radial gap betweenthe seal member (e.g., angel wing seal) and the discourager seal canhelp to reduce fluid flow losses in the working fluid section of theturbomachine. Additionally, the use of a plasma generator for thispurpose allows for preservation of the clearance between the seal memberand the discourager seal when the turbomachine is not operating (or whenthe plasma generator is not actuated). This clearance is conventionallyreferred to as the “cold” clearance, which implies that it exists whenthe turbomachine is not running. The plasma generator-based clearancemanagement solution described according to embodiments of the inventionallows for reduction of the “hot” (during operation) clearance betweenthe seal member and discourager seal, without negatively affecting thecold clearance between these components.

Turning to FIG. 1, a cross-sectional schematic view of a section of aturbomachine 2 is shown according to various embodiments of theinvention. As with conventional turbomachines, the turbomachine 2 caninclude a diaphragm section 4, which forms part of the stator section(not shown) of the turbomachine 2. The diaphragm section 4 remainsgenerally static during operation of the turbomachine 2. Also shown, theturbomachine 2 can include a rotor section 6, which is positionedradially inward of the diaphragm 4 (where portions of the diaphragmsection 4 and rotor section 6 radially overlap). As referred to herein,the terms radial, radially, etc., refer to the relative position ofcomponents in the radial direction (r), which runs substantiallyperpendicular to the axis of rotation (A) of the rotor section 6. Theterms axial, axially, etc., refer to relative positions of components inthat axial (A) direction.

Returning to FIG. 1, the diaphragm section 4 can include an axiallyfacing wall 8 (several labeled), and a discourager seal 10 protrudingaxially from the axially facing wall 8. The discourager seal 10 can beformed of a conventional seal material, e.g., a durable composite, ametal such as steel, etc. In some cases, the discourager seal issubstantially planar, e.g., planar on its radially outward facing andradially inward facing sides. Several discourager seals 10 are shown inFIG. 1, because, as will be understood by those having skill in the art,the turbomachine 2 can include a plurality of stages, each with a pairof discourager seals 10.

The rotor section 6 can include a bucket 14 (more than one shown) withan axially facing wall 16 opposing the axially facing wall 8 of thediaphragm section 4. These axially facing walls 8, 16 help to form afluid channel 18 (also referred to as a non-linear fluid channel herein)which spans from a primary fluid (e.g., working fluid) section 20 of theturbomachine 2 to a secondary fluid (e.g., cooling fluid) section 22 ofthe turbomachine 2. The rotor section 6 can further include a sealmember 24 extending from the axially facing wall 16 of the bucket 14.The seal member 24 can be formed as a conventional “angel-wing” sealmember, which can include an axially extending portion 26 and a radiallyextending portion 28 connected with (e.g., continuous with) the axiallyextending portion 26 (only partially labeled in some circumstances forclarity of illustration). In various embodiments the seal member 24 isan integral component without discernible distinction between theaxially extending portion 26 and the radially extending portion 28.

The seal member 24 axially overlaps (along axis A) a portion of thediscourager seal 10, such that a line running parallel with the radialdirection (r) (or, perpendicular to the axis A) can intersect a portionof the seal member 24 and the discourager seal 10. Between the sealmember 24 and the discourager seal 10 is a radial gap 30. As describedherein, various embodiments of the invention are directed towardpartially closing or reducing the size of that radial gap 30.

The turbomachine 2 can further include a plasma generator (PG) 32coupled to the diaphragm section 4. The plasma generator 32 can becoupled, e.g., physically affixed to, embedded within, housed within,etc., the diaphragm section 4 at any suitable location for performingthe plasma generation functions described herein. In particularembodiments, the plasma generator 32 can be coupled (e.g., physicallyconnected) to the discourager seal 10. The plasma generator 32 can beconfigured to generate a plasma (FIG. 2) to reduce the radial gap 30between the seal member 24 and the discourager seal 10 (e.g., to preventflow of fluid from the secondary flow section 22 to the primary flowsection 24). In various embodiments, the plasma can reduce a radialdistance between the radially extending portion 28 of the seal member 24and the discourager seal 10. In some cases, the plasma can reduce anaxial clearance between the discourager seal and the radially extendingportion 28 of the seal member 24. Two dashed lines are shown in FIG. 1and FIG. 2 to illustrate electrical connection between components in theplasma generator PG 32.

As shown, the bucket 14 can further include a base section 36 and ablade 38 extending radially from the base section 36. The base section36 can include the axially facing surface 16 of the bucket 14. Thediaphragm section 4 can also include at least one nozzle 37, whichinteracts with the blade 38 to guide a working fluid (e.g., gas) overthe face of the blade 38.

FIG. 2 shows a schematic close-up view of a portion of the turbomachine2 of FIG. 1, with particular focus on the plasma generator 32,discourager seal 10 and the seal member (or, angel wing seal) 24. Asshown, the plasma generator 32 can include a dielectric 40 (plasmadielectric) which can be attached to the radially inwardly facingsurface of the discourager seal 10. The plasma dielectric 40 can beformed of any conventional plasma dielectric material. The plasmagenerator 32 can also include an embedded electrode 42 within thedielectric 40. The embedded electrode 42 can be formed of a conventionalelectrode metal, e.g., copper, tungsten, etc. The plasma generator 32can further include an exposed electrode 44 outside of the dielectric40, positioned radially inboard of the dielectric 40. The plasmagenerator 32 can further include a current supply 46 for applying acurrent (e.g., an alternating current, or AC current) to the embeddedelectrode 42 and the exposed electrode 44 to generate a plasma 46 (byconverting the secondary fluid flow 22 to plasma) across the radiallyinwardly facing surface of the plasma dielectric 40. The plasma 46 canaid in reducing the distance (radial gap 30) between the discouragerseal 10 and the seal member 24, in particular, the distance between thetip of the radially extending portion 28 of the seal member 24 and thediscourager seal 10.

As noted herein, the plasma generator 32 includes the embedded electrode42 and the exposed electrode 44, separated by the plasma dielectric 40.The plasma dielectric 40 is exposed to the secondary flow 22 as it flowsthrough the turbomachine 2. The current (e.g., AC current) supply 46 isconnected to the electrodes to supply a high voltage AC potential to theelectrodes 42, 44.

When the AC amplitude is large enough, the secondary flow 22 ionizes ina region of largest electric potential forming the plasma 46. The plasma46 generally begins at an edge 48 of the exposed electrode 44, which isexposed to the secondary flow 22 and spreads out over an area projectedby the exposed electrode 44 which is covered by the plasma dielectric30. The plasma 46 in the presence of an electric field gradient producesa force on the gas flow 22 located between the seal member 24 and theplasma 46, inducing a virtual aerodynamic shield which helps to preventsecondary flow 22 from entering the primary flow 20 of the turbomachine2.

Various embodiments of the invention relate to a method of forming aplasma on a turbomachine (e.g., turbomachine 2) to at least partiallyseal a gap between components of the turbomachine. FIG. 3 shows anillustrative flow diagram including processes in a method of forming aplasma to at least partially seal a gap between turbomachine components.One having skill in the art will understand that the processes shown anddescribed with reference to FIG. 3 can be applied to one or more systemssimilar to those shown and described with reference to FIG. 1, FIG. 2 orsimilar systems. As shown, the method can include the followingprocesses:

Process P1: Providing a turbomachine having: a diaphragm section having:an axially facing wall; and a discourager seal protruding axially fromthe axially facing diaphragm wall; a rotor section having: a buckethaving an axially facing wall opposing the axially facing wall of thediaphragm section; and a seal member extending from the axially facingwall of the bucket, wherein the seal member axially overlaps a portionof the discourager seal of the diaphragm section leaving a radial gapbetween the seal member and the discourager seal; and a plasma generatorcoupled to the diaphragm section; and

Process P2: Actuating the plasma generator to generate a plasma whichreduces the radial gap between the seal member and the discourager seal.It is understood that the process of actuating the plasma generatorincludes initiating generation of the plasma, e.g., by increasing an ACcurrent supplied to the electrodes 42, 44 via a dial, switch, or othermechanism. It is further understood that the plasma can also reduce theaxial clearance between the discourager seal and the radially extendingportion of the seal member, helping to prevent the secondary flow fromentering the primary flow of the turbomachine.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. It is further understood that theterms “front” and “back” are not intended to be limiting and areintended to be interchangeable where appropriate.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

We claim:
 1. A turbomachine comprising: a diaphragm section having: anaxially facing diaphragm wall; and a discourager seal protruding axiallyfrom the axially facing diaphragm wall; a rotor section having: a buckethaving an axially facing bucket wall opposing the axially facingdiaphragm wall; and a seal member extending from the axially facingbucket wall, wherein the seal member axially overlaps a portion of thediscourager seal of the diaphragm section leaving a radial gap betweenthe seal member and the discourager seal; and a plasma generator coupledto the diaphragm section for generating a plasma which reduces theradial gap between the seal member and the discourager seal.
 2. Theturbomachine of claim 1, wherein the seal member includes: an axiallyextending portion; and a radially extending portion continuous with theaxially extending portion.
 3. The turbomachine of claim 2, wherein theplasma reduces a radial gap between the radially extending portion andthe discourager seal.
 4. The turbomachine of claim 1, wherein thediscourager seal is substantially planar.
 5. The turbomachine of claim1, wherein the bucket further includes a base section and a bladeextending radially from the base section, wherein the base sectionincludes the axially facing bucket wall.
 6. The turbomachine of claim 1,wherein the plasma generator is coupled to the discourager seal.
 7. Theturbomachine of claim 1, wherein the plasma generator includes: adielectric; an embedded electrode within the dielectric; an exposedelectrode outside of the dielectric; and a current supply for applying acurrent to the embedded electrode and the exposed electrode.
 8. Theturbomachine of claim 7, wherein the dielectric is located on a radiallyinwardly facing surface of the discourager seal.
 9. The turbomachine ofclaim 8, wherein the plasma generator is configured to generate theplasma on a radially inwardly facing surface of the dielectric.
 10. Theturbomachine of claim 1, wherein the discourager seal is locatedradially outward of the seal member.
 11. A turbomachine comprising: adiaphragm section having: an axially facing diaphragm wall; and adiscourager seal protruding axially from the axially facing diaphragmwall; a rotor section having: a bucket having an axially facing bucketwall opposing the axially facing diaphragm wall; and a seal memberextending from the axially facing bucket wall, wherein the seal memberaxially overlaps a portion of the discourager seal of the diaphragmsection leaving a radial gap between the seal member and the discouragerseal; a fluid channel extending between the axially facing diaphragmwall and the axially facing bucket wall, the fluid channel intersectingwith the radial gap; and a plasma generator coupled to the diaphragmsection for generating a plasma which reduces the radial gap between theseal member and the discourager seal.
 12. The turbomachine of claim 11,wherein the seal member includes: an axially extending portion; and aradially extending portion continuous with the axially extendingportion.
 13. The turbomachine of claim 12, wherein the plasma reduces aradial gap between the radially extending portion and the discouragerseal.
 14. The turbomachine of claim 11, wherein the discourager seal issubstantially planar.
 15. The turbomachine of claim 11, wherein thebucket further includes a base section and a blade extending radiallyfrom the base section, wherein the base section includes the axiallyfacing bucket surface.
 16. The turbomachine of claim 11, wherein theplasma generator is coupled to the discourager seal.
 17. Theturbomachine of claim 11, wherein the plasma generator includes: adielectric; an embedded electrode within the dielectric; an exposedelectrode outside of the dielectric; and a current supply for applying acurrent to the embedded electrode and the exposed electrode.
 18. Theturbomachine of claim 17, wherein the dielectric is located on aradially inwardly facing surface of the discourager seal, wherein theplasma generator is configured to generate the plasma on a radiallyinwardly facing surface of the dielectric.
 19. The turbomachine of claim18, wherein the plasma interferes with fluid flow from the fluid channelthrough the radial gap.
 20. A method comprising: providing aturbomachine having: a diaphragm section having: an axially facingdiaphragm wall; and a discourager seal protruding axially from theaxially facing diaphragm wall; a rotor section having: a bucket havingan axially facing bucket wall opposing the axially facing diaphragmwall; and a seal member extending from the axially facing bucket wall,wherein the seal member axially overlaps a portion of the discouragerseal of the diaphragm section leaving a radial gap between the sealmember and the discourager seal; and a plasma generator coupled to thediaphragm section; and actuating the plasma generator to generate aplasma which reduces the radial gap between the seal member and thediscourager seal, wherein the plasma further reduces an axial gapbetween the discourager seal a radially extending portion of the sealmember.